Capacitive Accelerometer Electrostatic Force Compensation
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Solution Overview
Problem
Capacitive accelerometers face challenges due to manufacturing imperfections and electrostatic forces that degrade the precision of acceleration measurements, particularly in terms of parasitic capacitance and electrostatic interference.
Innovation Solution
A capacitive accelerometer design with electrostatic force compensation means, utilizing a mobile electrode and voltage sources to generate and compensate for missing electrostatic forces, allowing for reliable calibration and reduced power consumption by adjusting the charge transfer rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electrostatic force compensation means are added to cancel parasitic signals, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent merges the measurement function and electrostatic force compensation function into a single integrated device. The first and second capacitors simultaneously serve as both measurement elements and electrostatic force generation elements. By applying voltages to these capacitors, the device generates electrostatic forces on the mobile electrode to compensate for parasitic signals, thereby eliminating the need for separate compensation mechanisms and reducing overall device complexity.
Solution Approach 2:
The first and second capacitors perform multiple functions: they serve as the primary measurement capacitors for detecting acceleration-induced capacitance changes, and simultaneously function as electrostatic force generation elements for compensating parasitic signals. This multi-functionality approach allows a single structural element to address both measurement and compensation requirements, improving precision without proportionally increasing complexity.
2Use of energy by moving object
If charge transfer rate is reduced to save power, then energy consumption is improved, but measurement precision deteriorates due to missing electrostatic force compensation
Solution Approach 1:
The patent applies electrostatic forces to the mobile electrode in advance of the actual acceleration measurement. By pre-positioning the mobile electrode using controlled electrostatic forces from the first and second capacitors, the system compensates for parasitic capacitance effects before the measurement phase begins. This preliminary compensation action ensures that subsequent measurements at reduced charge transfer rates remain precise, as the parasitic signal offset has already been corrected.
Solution Approach 2:
The system employs periodic charge transfer cycles that include both measurement phases and electrostatic force compensation phases. During periodic intervals, voltages are applied to generate compensating electrostatic forces, and during other intervals, capacitance measurements are taken. This periodic alternation between compensation and measurement allows the system to maintain precision while reducing the overall charge transfer rate and power consumption compared to continuous high-rate operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively cancels out parasitic signals, ensuring accurate acceleration measurements and reducing power consumption by maintaining electrostatic force consistency across varying capacitance sampling rates, facilitating easier calibration and improved signal-to-noise ratio.
Implementation Method 1
a first voltage source and a second voltage source for selectively applying a first voltage value to the first electrode, a second voltage value to the second electrode and a third voltage value to the third electrode, and arranged to generate electrostatic forces acting on the third electrode
Implementation Method 2
the third electrode is arranged to be displaced when the capacitive accelerometer is subject to acceleration thereby arranged to generate a capacitance difference value between the first and second capacitances transformable to electrical charges
Data Source
AI summary
A capacitive accelerometer for measuring an acceleration value is provided, including a first and a second electrode; a third mobile electrode arranged therebetween, and forming with the first electrode a first capacitor, and with the second electrode a second capacitor, the third electrode being displaced when the accelerometer is subject to acceleration and generates a capacitance difference value transformable to electrical charges; a first and a second voltage source configured to selectively apply first and second voltages to the first and the second electrodes, respectively, and a third voltage to the third electrode, and to generate electrostatic forces acting on the third electrode, the first, second and/or third voltages applied during electrical charge transfers for collecting the electrical charges to measure the acceleration; and an electrostatic force compensator to compensate for missing electrostatic forces due to a modified charge transfer rate, a compensation amount dependent on the modified rate.